Category Archives: Main engines

Marine engines description, troubleshooting and repairs

Understanding Engine Hydrostatic Locking: Causes, Prevention, and the Role of Marine Engineers

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In the world of marine engineering, hydrostatic locking is a term that sends shivers down the spine of every professional. It’s a potentially catastrophic problem that can lead to severe damage to engines and, in some cases, endanger the entire vessel. In this article, we will delve into the causes of engine hydrostatic locking, how it can be prevented, and the crucial role marine engineers play in ensuring it doesn’t reoccur.

What is engine hydrostatic locking?

Engine hydrostatic locking, also known as hydrolock, occurs when a liquid, usually water, enters the combustion chamber or cylinders of an engine, preventing the engine from turning over. This unwanted intrusion of liquid disrupts the engine’s internal workings, and in the case of a marine engine, it can spell disaster for the entire vessel.

Example of oil present into engine intake manifold. Source and credit: dieselmarineinsights.blogspot.com

For example, hydrolock happens when a volume of liquid greater than the volume of the cylinder at its minimum (end of the piston’s stroke) enters the cylinder. Since liquids are nearly incompressible, the piston cannot complete its travel; either the engine must stop rotating or a mechanical failure must occur.

Causes of Engine Hydrostatic Locking

The most common cause of hydrolocking in marine engines is water ingress through the exhaust system. This can happen if the exhaust outlet is submerged due to waves, trim, or loading conditions. Water can also enter the engine through the air intake, fuel system, or cooling system due to leaks, flooding, or condensation.

Depending on how much water is in the cylinders and how fast the engine is running, hydrolocking can have different effects on the engine. If the engine is stopped or idling, hydrolocking may cause the engine to stall or refuse to start. If the engine is running at high speed, hydrolocking may cause a loud noise and a sudden stop of the engine. The sudden expansion of gases can also cause gaskets to blow or cylinders to crack. The most common damage caused by hydrolocking is bent or broken connecting rods, which connect the pistons to the crankshaft.

Bent connecting rod. Source and credit: dieselmarineinsights.blogspot.com

Bent connecting rod. Source and credit: dieselmarineinsights.blogspot.com

Apart from water, when the engine is off, and there’s an intake leak, other fluids (oil, fuel) can easily enter the cylinders.

Prevention of Engine Hydrostatic Locking

  • Regular Maintenance: The most crucial step in preventing engine hydrolock is regular maintenance. This includes:
    • Checking and changing air filters, inspecting seals and valves for leaks, and ensuring that the engine is in optimal working condition.
    • Check and maintain the exhaust system regularly. Install anti-siphon devices or water traps to prevent water from flowing back into the engine.
    • Check and maintain the air intake system regularly. Make sure that the air filter is clean and dry and that there are no obstructions or leaks in the ducts or hoses. Avoid operating the engine in areas with high humidity or spray.
    • Check and maintain the fuel system regularly. Make sure that the fuel tank is vented properly and that there are no leaks or contamination in the lines or injectors. Use fuel additives to prevent water from accumulating in the fuel.
    • Check and maintain the cooling system regularly. Make sure that the coolant level is adequate and that there are no leaks or corrosion in the radiator, hoses, or pump. Use antifreeze to prevent freezing and boiling of the coolant.
  • Proper Ventilation: Adequate ventilation in the engine room can help reduce condensation and the risk of hydrolock. Proper ventilation systems can also help keep the engine room dry.
  • Water-Tight Integrity: Ensuring that the vessel is properly sealed and that water cannot enter the engine room in the event of flooding is essential. Make sure that the exhaust outlet is above the waterline and that there are no leaks or cracks in the pipes or valves. Regular inspections for potential breaches are crucial. Avoid operating the engine in extreme weather conditions or rough seas. Reduce speed and load when encountering waves or wakes. Monitor the engine temperature and pressure gauges and listen for any unusual sounds or vibrations.
  • Proper Shutdown Procedures: When shutting down the engine, it’s important to follow the manufacturer’s recommended procedures. This may include turning off the fuel supply before stopping the engine, preventing the intake of water during the cooling down process.

The Role of Marine Engineers

Marine engineers are responsible for designing, installing, operating, and maintaining marine engines and related systems. They play a vital role in preventing hydrostatic locking by ensuring that the engines are suitable for marine applications and that they meet safety and performance standards. Their responsibilities include:

  • Regular Inspections: Marine engineers should conduct regular inspections to identify and address potential issues that may lead to hydrolock. This includes inspecting intake systems, seals, and valves.
  • Maintenance: They are responsible for the routine maintenance of the engine, ensuring that air filters are changed, seals are in good condition, and the engine is functioning optimally.
  • Emergency Response: In the event of flooding or water intrusion, marine engineers must act swiftly to prevent or mitigate hydrolock. This may involve sealing off the affected area, pumping out water, and assessing and repairing any damage. They use their knowledge and skills to troubleshoot and resolve any issues related to hydrostatic locking or other engine malfunctions.

    Broken liner. Source and credit: dieselmarineinsights.blogspot.com

  • Training: Owners must ensure that the vessel’s engineering crew is trained to follow proper shutdown procedures and respond effectively in emergency situations. Marine engineers also educate and train other crew members on how to operate and maintain marine engines properly. They provide guidance and instructions on how to prevent hydrostatic locking and what to do in case it happens. They also follow emergency procedures and protocols to minimize damage and ensure safety in case of hydrostatic locking or other engine failures.

In conclusion, engine hydrostatic locking is a serious concern in the world of marine engineering. By understanding its causes and taking proactive steps to prevent it, marine engineers can safeguard the vessel and its crew. Their vigilance in regular maintenance, proper shutdown procedures, and rapid response to emergencies can make all the difference in ensuring the smooth operation of marine engines and the safety of everyone on board.

You can read a very interesting case study related to engine failure due hydrolocking if you follow THIS LINK.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World, Telegram Chief Engineer’s Log Chat or Instagram and will try to answer to all your queries. You can use the feedback button as well!

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Enhancing Marine Engine Efficiency: A Solution for Low-Speed Operation

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Author: Daniel G. Teleoaca – Marine Chief Engineer

Marine engines are the unsung heroes of the shipping industry, tirelessly powering vessels across vast oceans and seas.

However, these workhorses face a unique challenge when it comes to low-speed operation. Low speed operation can cause various problems for marine engines, such as increased fuel consumption, reduced power output, higher emissions, and more wear and tear. The inefficiency of marine engines at lower speeds can have significant economic and environmental implications.

Preceding the implementation of emission-limiting regulations, some of the ships, especially containers, were generally engineered to achieve maximum cruising velocities of 30 knots. Presently, operators are obligated to comply with regulatory frameworks such as the carbon intensity indicator (CII) and the energy efficiency existing ship index (EEXI).

As a consequence, cruising veers off at approximately 18 knots, which is roughly two-thirds the speed for which the engines were originally designed. As a result, engines operate extremely inefficiently at low loads, consuming significantly more fuel and emitting significantly more CO2 than is required.

Without intervention, Wartsila predicted in 2022 that by 2023, over one-third of container ships would be non-compliant, based on an analysis of the global fleet. Moreover, in the absence of intervention, 80% of container ships will be classified under the lowest CII category by 2030.

In this article, we’ll explore the reasons behind this inefficiency and the options available to improve marine engine performance when running at low speeds.

Understanding the Inefficiency

Marine engines are designed to operate at a certain range of speed and load, depending on the type and size of the engine, the ship’s hull form, the propeller characteristics, and the operating conditions. When the engine operates outside this range, it can suffer from inefficiency and performance loss. There are several key reasons for this inefficiency:

  • Reduced Combustion Efficiency: A cause of marine engine inefficiency at low speed is the incomplete combustion of fuel in the cylinders. The combustion process in a marine engine depends on many factors, such as the fuel quality, the air-fuel ratio, the injection timing, the compression pressure, the ignition temperature, and the combustion duration. When the engine operates at low speed and load, some of these factors can be adversely affected, resulting in incomplete combustion of fuel. Incomplete combustion can lead to lower power output, higher fuel consumption, higher emissions of carbon monoxide (CO), hydrocarbons (HC), particulate matter (PM), and smoke, and more carbon deposits in the cylinders and turbocharger.

  • Mechanical Losses: At low speeds, the engine’s mechanical components, such as pistons, bearings, and crankshafts, experience higher frictional losses. This additional resistance leads to decreased engine efficiency. Moreover, the turbocharger is a device that uses the exhaust gas from the engine to drive a compressor that increases the air pressure and density in the intake manifold. The turbocharger improves the engine performance by allowing more air and fuel to be burned in each cylinder. The turbocharger efficiency depends on the pressure ratio between the exhaust gas and the intake air, which is called the boost pressure. The boost pressure is highest at high engine speed and load, when there is more exhaust gas available to drive the turbocharger. When the engine operates at low speed and load, there is less exhaust gas available, and the boost pressure drops. This means that less air is supplied to the cylinders, resulting in lower power output, higher fuel consumption, higher emissions of nitrogen oxides (NOx), and more turbo lag.

  • Propeller Inefficiency: One of the main causes of marine engine inefficiency at low speed is the mismatch between the engine and the propeller. The propeller is a device that converts the rotational energy of the engine into thrust force for propulsion. The propeller efficiency depends on the ratio of the propeller speed to the ship speed, which is called the advance ratio. The propeller efficiency is highest at a certain advance ratio, which corresponds to a certain engine speed and load. When the ship operates at low speed, the advance ratio increases, and the propeller efficiency decreases. This means that more engine power is wasted as friction and turbulence in the water, rather than converted into useful thrust.

Therefore, the effects of marine engine inefficiency at low speed can be summarized as follows:

  • Lower power output: The engine produces less power than it is capable of, resulting in lower ship speed or lower reserve power for maneuvering or emergency situations.
  • Higher fuel consumption: The engine consumes more fuel than it needs to produce a given amount of power, resulting in higher operating costs and lower profitability.
  • Higher emissions: The engine emits more pollutants than it should, resulting in environmental damage and potential non-compliance with emission regulations.
  • More wear and tear: The engine suffers from more stress and damage due to friction, corrosion, erosion, vibration, overheating, fouling, etc., resulting in higher maintenance costs and lower reliability.

Options to improve marine engine efficiency and performance at low speed

The inefficiency of marine engines at low speeds is a persistent challenge, but there are several innovative solutions available to mitigate this issue. Some of these options are:

  • Variable Geometry Turbochargers (VGTs): VGTs are turbochargers that can adjust their geometry to optimize airflow at different engine speeds. They help maintain higher combustion efficiency, even at low speeds, reducing fuel consumption and emissions.

  • Slow Steaming Strategies: Slow steaming involves deliberately operating a vessel at reduced speeds to conserve fuel. It has become a popular strategy in the shipping industry, allowing ships to run more efficiently at lower RPMs, thus saving fuel.

  • Dual-Fuel Engines: Dual-fuel engines are designed to run on a combination of natural gas and diesel fuel. These engines offer improved combustion efficiency and emissions control, making them an attractive option for low-speed operation.

  • Waste Heat Recovery Systems: Waste heat recovery systems capture and reuse the heat generated by the engine’s exhaust. They can be used to produce additional power or drive other ship systems, enhancing overall energy efficiency.

  • Upgraded Propellers: Shipowners can consider investing in more efficient propeller designs, specifically tailored to their vessels’ operating profiles. Modern propeller designs are more adaptable to a wide range of ship speeds.

  • Improved Hull Design: The vessel’s hull design can also impact its performance at lower speeds. Optimized hull shapes can reduce hydrodynamic resistance and improve overall efficiency.

  • Hybrid Power Systems: Some vessels employ hybrid power systems that combine traditional diesel engines with electric propulsion. This setup allows for efficient power delivery at various speeds, including low-speed operation.

  • Engine derating: Engine derating is a method of reducing the maximum power output of an engine by adjusting its settings or components. Engine derating can improve the engine efficiency at low speed by reducing the mismatch between the engine and the propeller, and by optimizing the combustion process and the turbocharger operation. Engine derating can also reduce the emissions of NOx, CO, HC, and PM. However, engine derating can also reduce the reserve power of the engine, and may require the approval of the engine manufacturer and the classification society.
  • Turbocharger cut-out: Turbocharger cut-out is a method of disconnecting one or more turbochargers from an engine by closing a valve or opening a bypass. Turbocharger cut-out can improve the engine efficiency at low speed by increasing the boost pressure and the air supply to the cylinders. Turbocharger cut-out can also reduce the emissions of CO, HC, and smoke. However, turbocharger cut-out can also increase the emissions of NOx, and may cause the turbocharger to overheat or surge.

In conclusion, addressing the inefficiency of marine engines at low speeds is critical for both economic and environmental reasons. The shipping industry has made significant strides in developing technologies and strategies to improve engine efficiency during slow steaming and low-speed operation. These solutions not only reduce fuel consumption but also contribute to lower emissions and a more sustainable maritime industry. As technology continues to advance, marine engines are likely to become more versatile, making them more efficient across a broader range of operating speeds, ultimately benefiting the entire global shipping industry.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World, Telegram Chief Engineer’s Log Chat or Instagram and will try to answer to all your queries. You can use the feedback button as well!

If you like my posts, please don’t forget to press Like and Share. You can also Subscribe to this blog and you will be informed every time when a new article is published.

Also you can buy me a coffee by donating to this website, so I will have the fuel I need to keep producing great content! Thank you!

Demystifying Marine Engine Crankshaft Deflection Measurements: A Comprehensive Guide

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Marine engines are the heart of any seafaring vessel, powering them through the vast expanse of the ocean. Ensuring their optimal performance is crucial for the safety and efficiency of maritime operations. One vital aspect of marine engine maintenance is monitoring and interpreting crankshaft deflection measurements.

What is crankshaft deflection?

Crankshaft deflection refers to the measurement of the deviation or displacement in the centerline of the engine’s crankshaft from its ideal position during operation. It is a critical parameter that reflects the mechanical health and alignment of the engine components, particularly in large marine engines. Excessive crankshaft deflection can lead to fatigue, fracture, wear, and damage of the crankshaft and other engine components. Accurate interpretation of crankshaft deflection measurements helps prevent catastrophic failures and costly repairs, ultimately ensuring vessel safety.

If you want to learn more about crankshaft deflection please follow THIS LINK.

How to Measure Crankshaft Deflection

If you follow the above mentioned link, you will find an explanation with regard to deflection measurement.

Importance of Crankshaft Deflection Measurements

  • Early Problem Detection: Monitoring crankshaft deflection allows for early detection of mechanical issues or misalignments in the engine, preventing them from escalating into major problems that could lead to engine failure.

  • Safety Assurance: A properly aligned crankshaft is essential for the safety of the vessel and its crew. Correct alignment reduces the risk of catastrophic engine failures that could result in accidents at sea.

  • Enhanced Engine Efficiency: Correcting misalignments revealed by deflection measurements can significantly improve engine efficiency, reducing fuel consumption and environmental impact.

  • Cost Savings: Identifying and rectifying issues early on can save substantial repair and replacement costs in the long run, making crankshaft deflection measurements a cost-effective maintenance practice.

How to Interpret Marine Engine Crankshaft Deflection Measurements

Crankshaft deflection measurements are usually expressed as a table or a graph showing the values of deflection at different angular positions of the crankshaft for each unit.

Source and Credit: marineengineersknowledge.com

The values are compared with the manufacturer’s specifications and limits to assess the condition of the crankshaft.

Interpreting crankshaft deflection measurements requires a combination of technical knowledge and practical experience. Follow these steps to ensure accurate interpretation:

  • Understand the Measurement Units: Crankshaft deflection measurements are typically expressed in micrometers (µm) or millimeters (mm). Familiarize yourself with these units and their conversion to ensure precision in your interpretations. Moreover, the dial indicator should be calibrated and checked regularly for any errors or defects. A faulty dial indicator can give false readings and lead to incorrect interpretation of deflection measurements.

For example, in the table below, U1 means unit 1, T means top position, B means bottom position, F means fuel pump side position, and E means exhaust side position. The values are in mm.

Unit T B F E
U1 0 0 0 0
U2 -0.02 +0.02 -0.01 +0.01
U3 -0.04 +0.04 -0.02 +0.02
U4 -0.06 +0.06 -0.03 +0.03
U5 -0.08 +0.08 -0.04 +0.04
U6 -0.10 +0.10 -0.05 +0.05

Plot the deflection values on a graph for each unit, using a different color or symbol for each angular position. 

Source and Credit: Marineinbox

  • Establish Baseline Measurements: Before interpreting any measurements, it’s essential to establish baseline readings for the engine when it’s in perfect condition. These baseline measurements act as a reference for identifying deviations and can be found in the engine Technical File, under Shop Trial Measurements.

  • Examine Measurement Patterns: Crankshaft deflection measurements are usually taken at multiple points along the crankshaft’s length. Analyze these measurements to identify any recurring patterns or trends. Irregularities may indicate misalignments or mechanical issues.

    • Uniformity: This is when all units show similar values of deflection within acceptable limits. This indicates that the crankshaft is in good condition and aligned properly.
    • Sagging: This is when one or more units show higher values of deflection at either top or bottom positions, indicating that the crankshaft is bending downwards due to gravity or load.
    • Hogging: This is when one or more units show higher values of deflection at either top or bottom positions, indicating that the crankshaft is bending upwards due to gravity or load.
    • Twisting: This is when one or more units show higher values of deflection at either fuel pump side or exhaust side positions, indicating that the crankshaft is twisting along its axis due to torsional forces.
    • Ovality: This is when one or more units show higher values of deflection at all positions, indicating that the crankpin or journal has become oval-shaped due to excessive wear or damage.

  • Consider Operational Conditions: It’s vital to take into account the engine’s operational conditions during measurements. Factors like load, temperature, and RPM can influence deflection readings. Comparing measurements under different conditions can provide valuable insights.

For example, the crankshaft expands and contracts with changes in temperature, which can affect the deflection values. Therefore, it is recommended to measure the deflection at a consistent temperature, preferably when the engine is cold or after a short warm-up period.

Moreover, the draught of the vessel can cause bending or twisting of the hull, which can affect the alignment of the engine and the crankshaft. Therefore, it is recommended to measure the deflection at a consistent draught, preferably when the vessel is fully loaded or unloaded.

  • Consult Manufacturer Guidelines: Manufacturers of marine engines often provide guidelines for interpreting crankshaft deflection measurements specific to their engine models. These guidelines should be consulted and followed diligently.

    • If they are within tolerance, then no action is required.
    • If they are out of tolerance, then corrective action is needed.

For example, in the table below, the manufacturer’s specifications and limits are given as:

    • Maximum permissible difference between top and bottom positions: 0.12 mm.
    • Maximum permissible difference between fuel pump side and exhaust side positions: 0.08 mm.
    • Maximum permissible difference between adjacent units: 0.04 mm.
Unit T-B Difference (mm) F-E Difference (mm) Adjacent Unit Difference (mm)
U1 0 0 N/A
U2 0.04 0.02 0.02
U3 0.08 0.04 0.02
U4 0.12 0.06 0.02
U5 0.16 0.08 0.02
U6 0.20 0.10 0.02

In this example, units U1, U2, and U3 are within tolerance, while units U4, U5, and U6 are out of tolerance. Therefore, corrective action is needed for units U4, U5, and U6.

  • Seek Expert Advice: If you’re unsure about the interpretation of deflection measurements or suspect a significant issue, it’s advisable to consult with experienced marine engineers or specialists. Their expertise can help pinpoint problems accurately.

  • Regularly Monitor and Document: Maintain a comprehensive record of all deflection measurements and their interpretations. Regular monitoring allows you to track the engine’s health over time and detect any changes or deterioration.

    Identify the possible causes and solutions for the crankshaft deflection problems, based on the shape and pattern of the graph and the manufacturer’s recommendations.

    • If the graph shows sagging or hogging, it could be caused by uneven wear of main bearings, misalignment of engine foundation, or distortion of hull structure. The possible solutions are adjusting or replacing main bearings, aligning engine foundation, or correcting hull deformation.
    • If the graph shows twisting, it could be caused by uneven firing pressures, faulty fuel injection system, or misalignment of driven unit. The possible solutions are repairing fuel injection system, adjusting firing pressures, or aligning driven unit.
    • If the graph shows ovality, it could be caused by improper lubrication, journal bearing failure, overspeeding or overloading of engine, excessive crankshaft deflection and misalignment of parts. The possible solutions are replacing crankpin or journal, improving lubrication system, reducing engine speed or load, or correcting crankshaft deflection and alignment.

In conclusion, interpreting marine engine crankshaft deflection measurements is a critical aspect of engine maintenance, ensuring vessel safety, efficiency, and cost-effectiveness. By understanding the importance of these measurements and following the steps outlined in this guide, marine engineers and ship operators can effectively monitor and maintain their engines, ensuring smooth and trouble-free voyages on the high seas.

The Importance of Air Seals on Main Engine Exhaust Valves

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In the world of engineering and machinery, precision and reliability are paramount. One critical component that plays a vital role in ensuring the efficiency and performance of a combustion engine is the exhaust valve. To optimize the functioning of this crucial part, engineers have developed air seals that help maintain a secure and efficient seal. In this blog post, we will explore the significance of air seals on main engine exhaust valves, the types of air seals used, and their role in enhancing engine performance.

The Main Engine Exhaust Valve: A Crucial Component

Before diving into the intricacies of air seals, it’s essential to understand the importance of the main engine exhaust valve in a combustion engine. In an internal combustion engine, whether it’s found in a car, a ship, or an industrial machine, the exhaust valve serves a fundamental purpose. The main engine exhaust valve is a vital component of a marine diesel engine that controls the timing and duration of the exhaust gas flow from the cylinder to the turbocharger. The exhaust valve consists of several parts, such as the spindle, the housing, the seat, the hydraulic cylinder, and the air cylinder. The air cylinder is a device that uses compressed air to close the exhaust valve against the hydraulic pressure that opens it. The air cylinder has a piston that moves up and down along with the spindle, creating an air spring effect that ensures a smooth and reliable operation of the exhaust valve.

The Challenge: Gas Leakage

One of the primary challenges in designing exhaust valves is preventing gas leakage. Inefficient sealing can lead to several adverse consequences, including:

  • Reduced Efficiency: Gas leakage results in a loss of engine efficiency, as the engine must work harder to compensate for the escaping exhaust gases.
  • Environmental Impact: Incomplete combustion due to gas leakage can lead to increased emissions, contributing to air pollution and environmental degradation.
  • Increased Fuel Consumption: Gas leakage forces the engine to burn more fuel to maintain power output, leading to higher operational costs.

Types of Air Seals

To address the issue of gas leakage, engineers have developed various types of air seals, each with its own unique characteristics and applications. The air seal is a device that prevents air leakage from the air cylinder to the exhaust valve housing. It is made of a metallic outer ring and a rubber seal that contacts the spindle. The seal can have different shapes depending on the type of valve. The air seal is important for maintaining the proper air pressure and spring force in the air cylinder, as well as for protecting the spindle from corrosion and fouling by the exhaust gas. A faulty or worn-out air seal can cause air loss, reduced performance, increased fuel consumption, and higher emissions.

Exhaust valve air piston seal ring overhaul. Source and Credit: Rheinstinitz Karl Caler

Here are some common types of air seals used in main engine exhaust valves:

  • Floating Ring Seals: Floating ring seals consist of two concentric rings, with the outer ring rotating along with the valve. This design helps create a dynamic seal, minimizing gas leakage.
  • Poppet Valve Seals: Poppet valves are commonly used in internal combustion engines. They employ a cylindrical plug to control gas flow. Air seals in poppet valves help ensure a tight fit between the valve and the valve seat, preventing gas leakage.
  • Rotary Valve Seals: Rotary valves, found in some engines like rotary engines and two-stroke engines, use rotary seals to maintain a seal as the valve rotates. These seals play a crucial role in preventing gas leakage.
  • Labyrinth Seals: Labyrinth seals consist of intricate channels and ridges that create a tortuous path for gas to escape. This design effectively reduces gas leakage by increasing the distance exhaust gases must travel before exiting.

The Role of Air Seals in Enhancing Engine Performance

Air seals on main engine exhaust valves are vital for several reasons:

  • Gas Tightness: The primary function of air seals is to maintain gas tightness within the combustion chamber. This ensures that exhaust gases exit through the designated path, optimizing engine efficiency.
  • Reduced Emissions: By minimizing gas leakage, air seals contribute to lower emissions. This is especially critical in modern engines to meet stringent environmental regulations.
  • Improved Fuel Efficiency: A well-sealed exhaust valve reduces the engine’s workload, leading to improved fuel efficiency and reduced operational costs.
  • Enhanced Engine Longevity: Air seals help protect the engine from excessive wear and tear, prolonging its operational life.

The air seal on the main engine exhaust valve is a simple but important device that ensures efficient and safe operation of the engine. Therefore, it is essential to inspect and replace the air seal regularly as per the maker’s recommendations.

Example of exhaust valve overhauling. Source and Credit: DG E LEARING ADU ACADEMY

In conclusion, in the intricate world of internal combustion engines, even the smallest components play a critical role in ensuring performance and efficiency. Air seals on main engine exhaust valves are a testament to the precision and engineering prowess required to design and maintain these complex machines. By preventing gas leakage, these seals contribute to reduced emissions, improved fuel efficiency, and increased engine longevity. As technology continues to advance, we can expect further innovations in air seal designs, driving the continuous improvement of combustion engines in various applications.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World, Telegram Chief Engineer’s Log Chat or Instagram and will try to answer to all your queries. You can use the feedback button as well!

If you like my posts, please don’t forget to press Like and Share. You can also Subscribe to this blog and you will be informed every time when a new article is published.

Also you can buy me a coffee by donating to this website, so I will have the fuel I need to keep producing great content! Thank you!

U-Tube Manometer: Crucial Instrumentation for Main Engine Air Coolers and Turbochargers

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In the intricate world of marine engineering, the efficient operation of main engine air coolers and turbochargers is paramount to ensure the smooth functioning of a vessel’s propulsion system. These critical components are responsible for optimizing the combustion process and maintaining engine performance. To monitor and maintain these systems, marine engineers rely on essential instruments like U-Tube Manometers.

If you are familiar with marine diesel engines, you may have noticed that some of the components, such as the main engine air coolers and the turbochargers, are equipped with U-shaped glass tubes filled with liquid. These tubes are called U-tube manometers, and they are used to measure the pressure difference between two points in a fluid system.

Example of U-tube manometer on turbocharger

In this article, we will delve into the significance of U-Tube Manometers, why they are preferred over pressure gauges, their maintenance requirements, and troubleshooting tips. Understanding the importance of functional U-Tube Manometers on air coolers and turbochargers is vital for the safety and performance of a marine engine.

The Role of U-Tube Manometers

A U-tube manometer is a simple device that consists of a U-shaped glass/plastic tube containing liquid, usually water or oil.

The liquid level in each leg of the tube depends on the pressure applied to that leg. If both legs are exposed to the same pressure, such as atmospheric pressure, the liquid levels will be equal. However, if one leg is connected to a point of higher pressure, such as the inlet of an air cooler or a turbocharger, and the other leg is connected to a point of lower pressure, such as the outlet of an air cooler or a turbocharger, the liquid level in the high-pressure leg will drop, while the liquid level in the low-pressure leg will rise. The difference in liquid levels indicates the pressure difference between the two points.

So, the principle behind their operation is simple: as the differential pressure across the component changes, the liquid level in one arm of the U-tube rises while the other falls, providing a visual indication of the pressure difference.

U-tube manometers are used instead of pressure gauges for several reasons:

  • Direct Reading: One of the primary advantages of U-Tube Manometers is that they provide a direct reading of the differential pressure. Unlike pressure gauges that rely on mechanical elements, U-Tube Manometers offer a clear and instantaneous visual representation of the pressure difference, making them highly reliable. They are accurate and reliable, as they are not affected by temperature changes or mechanical vibrations.

  • Accuracy: U-Tube Manometers are known for their accuracy and precision in measuring pressure differentials. Pressure gauges may drift or require recalibration over time, while U-Tube Manometers maintain their accuracy as long as the liquid column remains stable. They do not require any external power source or calibration. They can measure both positive and negative pressures, as well as vacuum.

  • Durability: U-Tube Manometers are robust and durable instruments that can withstand harsh marine environments. They are less prone to damage compared to fragile pressure gauge dials and needles. Also, they are simple, cheap, and easy to install and operate.

Importance of Functional U-Tube Manometers

U-tube manometers are important because they provide a visual indication of the pressure difference across the air coolers and the turbochargers. This pressure difference reflects the performance and efficiency of these components, as well as the condition of the engine.

Example of U-tube manometer in main engine air cooler

For example, the main engine air cooler is a heat exchanger that cools down the compressed air from the turbocharger before it enters the engine cylinders. This increases the density and oxygen content of the air, which improves the combustion process and reduces emissions. The U-tube manometer connected to the air cooler shows the pressure drop across the cooler, which is proportional to the amount of heat transferred from the air to the cooling water. A low pressure drop indicates a low heat transfer rate, which means that either the air cooler is dirty or fouled, or that there is insufficient cooling water flow. A high pressure drop indicates a high heat transfer rate, which means that either the air cooler is clean and efficient, or that there is excessive cooling water flow.

U-Tube Manometers act as early warning systems. A sudden change in the pressure differential could indicate a problem with the air cooler or turbocharger, allowing engineers to take corrective actions before the issue escalates, potentially avoiding costly repairs and downtime.

By monitoring the U-tube manometers regularly, one can assess the performance and condition of the air coolers and turbochargers, and take appropriate actions to maintain or improve them.

Maintenance of U-Tube Manometers

U-tube manometers require little maintenance, but proper maintenance of U-Tube Manometers is essential to ensure their accuracy and reliability:

  • Liquid Column Inspection: Regularly inspect the liquid column in the U-tube for signs of contamination, evaporation, or air bubbles. Any irregularities can affect the accuracy of the readings and should be addressed promptly.

  • Leak Checks: They should be checked periodically for any leaks, cracks, clogs, or contamination. Ensure that the connections between the U-tube manometer and the monitored equipment are leak-free. Leaks can lead to false readings and should be sealed immediately.

  • Calibration: Periodically calibrate the U-Tube Manometer to confirm its accuracy. This calibration process may involve adjusting the liquid column height to a known reference value.

If any problems are detected with the U-tube manometers, they should be repaired or replaced as soon as possible.

Troubleshooting U-Tube Manometer Issues

When U-Tube Manometers are not functioning correctly, it can lead to inaccurate pressure readings. If there is any discrepancy between the readings of the U-tube manometers and other indicators of the engine performance, such as power output, fuel consumption, exhaust gas temperature, or emissions, one should investigate the possible causes and solutions.

Here are some common troubleshooting steps:

  • Check for Blockages: Inspect the tubing and connections for any blockages or obstructions that might impede the movement of the liquid in the U-tube.

    If both legs of the U-tube manometer show equal liquid levels, it means that there is no pressure difference across the component connected to the tube. This could indicate that either the component is blocked or bypassed, or that there is no flow through the component. One should check the valves, pipes, filters, and pumps related to the component, and ensure that they are open, clean, and working properly.

  • Verify Liquid Integrity: Ensure that the liquid inside the U-tube is in good condition and free from contamination. Replace the liquid if necessary.

  • Recheck Connections: Confirm that all connections are secure and that there are no leaks. Tighten or replace fittings as needed.

    If one leg of the U-tube manometer shows a higher liquid level than the other, it means that there is a negative pressure difference across the component connected to the tube. This could indicate that either the component is leaking or damaged, or that there is a backflow or reverse flow through the component. One should check the seals, gaskets, flanges, and clamps related to the component, and ensure that they are tight, intact, and aligned correctly.

  • Verify Liquid Column Stability: If the liquid column is fluctuating excessively, it could indicate air bubbles or evaporation. Replenish the liquid and remove any trapped air. If the liquid level in the U-tube manometer fluctuates or oscillates rapidly, it means that there is a pulsating or unstable pressure difference across the component connected to the tube. This could indicate that either the component is vibrating or resonating, or that there is a surge or stall in the flow through the component. One should check the mounts, supports, dampers, and silencers related to the component, and ensure that they are rigid, secure, and effective.

In conclusion, U-tube manometers must be always functional because they provide vital information about the pressure difference across the air coolers and turbochargers, which affects the engine performance and efficiency. If the U-tube manometers are not functional, one may not be able to detect any problems or faults with the air coolers and turbochargers, which could lead to serious consequences such as engine damage, power loss, fuel wastage, or emission violations. Therefore, it is essential to keep the U-tube manometers in good working condition and monitor them regularly.

In the challenging and dynamic environment of the open sea, having reliable instrumentation is not just a matter of convenience; it’s a matter of safety and operational efficiency.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World, Telegram Chief Engineer’s Log Chat or Instagram and will try to answer to all your queries. You can use the feedback button as well!

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The Necessity of Cutting Out One of the Vessel’s Main Engine Unit: A Comprehensive Guide for Marine Engineers

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Maintaining the efficient and safe operation of a vessel’s main engine units is crucial for smooth sailing and ensuring the safety of all onboard. In certain circumstances, it becomes necessary to cut out the combustion on or to isolate one of the main engine units. This article will delve into the process of cutting out combustion and isolating the unit, discuss when it is necessary, highlight the factors marine engineers need to consider, and outline the essential precautions and measures to be taken. The extent of the work to be carried out depends, of course, on the nature of the trouble.

Understanding the Process of Cutting Out Combustion

When a marine engineer decides to cut out the combustion on a main engine unit, it means intentionally stopping the fuel injection into that particular unit. By doing so, the engine’s power output is reduced, and it ceases to contribute to the propulsion of the vessel. This process involves a systematic and controlled approach to ensure the safety and functionality of the remaining operational units.

When is it Necessary to Cut Out Injection on a Main Engine Unit?

There are several scenarios in which cutting out the injection on a main engine unit becomes necessary:

    • Technical Malfunctions: In the event of a malfunction or breakdown in one of the main engine units, cutting out the combustion allows the crew to isolate the faulty unit and prevent further damage. This ensures the vessel can continue its operations with the remaining functional engines. The technical malfunctions can be, for instance but not reduced to:
      • blow-by at piston rings or exhaust valve
      • bearing failures which necessitate reduction of bearing load
      • faults in the injection system.
    • Maintenance and Repairs: Routine maintenance and repair activities may require cutting out the combustion on a main engine unit. This allows the marine engineer to safely conduct necessary maintenance procedures, such as inspections, replacements, or repairs, without endangering the crew or vessel.
    • Fuel Economy and Efficiency: During periods of reduced power demand, such as when sailing at lower speeds or in calm waters, cutting out the combustion on one or more engine units can optimize fuel consumption and increase overall efficiency. This strategy helps minimize operating costs and extend the lifespan of the engines.

Process of Cutting Out Combustion on a Main Engine Unit

    • Initial Assessment: The marine engineer must conduct a thorough assessment of the engine to identify the specific unit requiring combustion cut-out. This includes analyzing performance data, monitoring alarm systems, and conducting visual inspections.

    • Preparing the Engine: Prior to cutting out combustion, the engineer needs to ensure the vessel is at a safe operating condition. This involves reducing the load on the affected unit and synchronizing the remaining engines, if required, for optimal performance.

    • Shutting Down Injection: Once the engine is prepared, the marine engineer can proceed with cutting out the injection on the designated unit. This is typically achieved by isolating the fuel supply, closing relevant valves, and activating the engine control system to cease fuel injection.

In case of camshaft type engine the injection can be cut out by lifting and securing the fuel pump roller guide. The entire procedure for cutting out the injection on one of the units is fully described in the engine manual.

Should the engine be kept running with the injection cut out for an extended period, the lubricating oil feed rate for the respective cylinder must be reduced to the minimum. If the piston and exhaust valve gear are still operational, do not shut down the piston cooling oil and cylinder cooling water on that particular unit.

In case of electronic controlled engines, cutting out the injection is more simpler as everything is done from the Engine Control Panel Unit.

You must be aware that with an injection pump cut out the engine can no longer be run at its full power.

Process of Combustion and Compression cut out. Piston still working in cylinder.

This measure is permitted in the event of, for instance, water is leaking into the cylinder from the cooling jacket/liner or cylinder cover.

The procedure is as follow:

    • Cut out the fuel pump by lifting and securing the roller guide.
    • Put the exhaust valve out of action and lock it in open position.
    • Shut-off the air supply to the exhaust valve, and stop the lube oil pumps. Dismantle and block the actuator oil pipe. Restart the lube oil pumps.
    • Close the cooling water inlet and outlet valves for the cylinder. If necessary, drain the cooling water spaces completely.
    • Dismantle the starting air pipe, and blank off the main pipe and the control air pipe for the pertaining cylinder.
    • When operating in this manner, the speed should not exceed 55% of MCR speed.

Note: The joints in the crosshead and crankpin bearings have a strength that, for a short time, will accept the loads at full speed without compression in the cylinder. However, to avoid unnecessary wear and pitting at the joint faces, it is recommended that, when running a unit continuously with the compression cut-out, the engine speed is reduced to 55% of MCR speed, which is normally sufficient to maneuver the vessel.
During maneuvers, if found necessary, the engine speed can be raised to 80% of MCR speed for a short period, for example 15 minutes.
Under these circumstances, in order to ensure that the engine speed is kept within a safe upper limit, the overspeed level of the engine must be lowered to 83 % of MCR speed.

Process of Combustion Cut Out. Exhaust Valve closed. Piston still working in cylinder.

This measure may be used if, for instance, the exhaust valve or the actuating gear is defective.

The procedure is as follow:

    • Cut out the fuel pump by lifting and securing the roller guide.
    • Put the exhaust valve out of action so that the valve remains closed (lift the guide or stop the oil supply and remove the hydraulic pipe).

Please note that, the cylinder cooling water and piston cooling oil must not be cut out.

Process of piston, piston rod, and crosshead suspended in the engine. Connecting rod out

This measure may be used if, for instance, serious defects in piston, piston rod, connecting rod, cylinder cover, cylinder liner and crosshead.

The procedure is as follow:

    • Cut out the fuel pump by lifting and fixing the roller guide.
    • Put the exhaust valve out of action so that the valve remains closed.
    • Dismantle the starting air pipe. Blank off the main pipe and the control air pipe for the pertaining cylinder.
    • Suspend the piston, piston rod and crosshead, and take the connecting rod out of the  crankcase.
    • Blank off the oil inlet to the crosshead.
    • Set the cylinder lubricator for the pertaining cylinder, to ‘ ‘zero’’ delivery.

Please note that, in this case the blanking-off of the starting air supply is particularly important, as otherwise the supply of starting air will blow down the suspended engine components.

Precautions and Measures for Cutting Out a Main Engine Unit

    • Safety Protocols: The utmost priority when cutting out a main engine unit is ensuring the safety of the vessel, crew, and engineers involved. Marine engineers must follow established safety protocols, wear appropriate personal protective equipment (PPE), and coordinate with the ship’s personnel to minimize risks during the procedure.

    • Communication and Coordination: Effective communication between the marine engineer, engine room crew, and bridge team is crucial. The bridge team must be aware of any changes in engine configuration to adjust vessel operations accordingly and maintain situational awareness.

    • Monitoring and Alarms: While cutting out combustion, continuous monitoring of engine parameters, alarms, and performance indicators is essential. Any unusual readings or abnormalities should be promptly reported and addressed to prevent further complications.

    • Documentation: It is vital to maintain comprehensive documentation throughout the process, including detailed reports of the engine condition, actions taken, and any observations made during the combustion cut-out. This information assists in analyzing the cause of the malfunction and aids in future maintenance planning.

In conclusion, cutting out the combustion on a main engine unit is a critical procedure that marine engineers may need to undertake to safeguard vessel operations and prevent further damage. Whether due to engine malfunction, contamination, or maintenance requirements, this process requires careful assessment, preparation, and adherence to safety protocols. By following the necessary precautions and measures, marine engineers can effectively isolate and address the issues affecting the main engine unit, ensuring the safety, efficiency, and reliability of the vessel’s propulsion system.

If you want to learn and get a “Diploma in Marine Diesel Engines”, please follow THIS LINK on Alison platform. The course is free and all you need to do is just to subscribe to their platform using the link above. This will be of a great help to me as well, as I will earn small commission. You can consider this as a reward for my effort to provide guidance and advices with regard to complex, challenging and rewarding marine engineering. 

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World, Telegram Chief Engineer’s Log Chat or Instagram and will try to answer to all your queries. You can use the feedback button as well!

If you like my posts, please don’t forget to press Like and Share. You can also Subscribe to this blog and you will be informed every time when a new article is published.

Also you can buy me a coffee by donating to this website, so I will have the fuel I need to keep producing great content! Thank you!

Marine Fuel Injector Valves – Ensuring Optimal Performance

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Marine fuel injectors are critical components of an engine’s fuel delivery system, responsible for precisely atomizing fuel and delivering it to the combustion chamber. Over time, these injectors can become clogged, worn, or develop leaks, resulting in decreased engine performance, reduced fuel efficiency, and potential engine damage. In this blog article, we will explore the importance of overhauling and maintaining marine fuel injectors to ensure their optimal performance and prolong the life of your marine engines.

Before diving into the overhaul and maintenance process, it’s crucial to be aware of common signs indicating potential fuel injector problems. These signs include: reduced engine power and acceleration, rough idling or stalling, increased fuel consumption, misfires or engine hesitation, smoke emissions from the exhaust, difficulty starting the engine etc. If you want to learn more about “How to check fuel injector valve condition”, please follow THIS LINK.

Marine engines are subject to strict emissions regulations aimed at minimizing their environmental impact. Maintaining the peak performance and efficiency of marine engines is crucial for a smooth sailing experience. Among the various components that play a pivotal role in engine function, fuel injectors stand out as critical elements. These small but mighty devices atomize fuel and deliver it to the engine’s combustion chamber, directly impacting its power, fuel economy, and emissions.

Fuel injectors must deliver fuel in a precise spray pattern and at the right pressure for efficient combustion. Over time, fuel injectors can develop leaks or clogs that disrupt this delicate balance, leading to suboptimal combustion. By conducting regular leak and pressure tests, marine engineers can identify and rectify any issues promptly. Maintaining the integrity of fuel injectors ensures that the engine receives the right amount of fuel, enhancing combustion efficiency, power output, and reducing fuel consumption.

Leaking fuel injectors can result in serious consequences for marine engines. When fuel leaks occur, excess fuel can infiltrate the engine’s oil system, diluting the lubricating properties of the oil and causing accelerated wear and tear on internal components. In extreme cases, uncontrolled fuel leaks can even lead to engine fires, posing a significant risk to the vessel and its crew. By performing regular leak tests, potential issues can be detected early, preventing costly engine damage and ensuring safe operation on the water.

When fuel injectors leak or malfunction, the combustion process is compromised, leading to incomplete fuel burn and increased emissions of pollutants such as hydrocarbons and nitrogen oxides. Regular leak and pressure tests help maintain optimal injector performance, ensuring cleaner combustion, and reducing the vessel’s environmental footprint.

Fuel injectors that are functioning optimally contribute to overall engine performance and reliability. A leak or malfunctioning injector can result in reduced engine power, rough idling, decreased throttle response, and even engine misfires. Through leak and pressure testing, any injector-related issues can be promptly identified and resolved, allowing the engine to operate at its full potential. A well-maintained fuel injection system ensures smooth operation, enhances engine reliability, and minimizes the risk of unexpected breakdowns.

Overhauling fuel injectors involves a thorough cleaning and restoration process to remove deposits, restore proper fuel flow, and optimize performance.

Here’s a step-by-step guide to overhauling marine fuel injectors:

    • Carefully remove the fuel injectors from the engine, following the manufacturer’s instructions.
    • Examine the injectors for any signs of damage, such as cracked or broken components. Check the injector tips for carbon buildup or clogging, which can impede fuel flow.
    • Utilize a specialized injector cleaning kit or professional cleaning service to remove deposits, varnish, and carbon buildup. Follow the specific instructions provided with the cleaning kit or consult manufacturer or a professional technician.
    • Replace worn or damaged injector components, such as O-rings, seals, and nozzles, to ensure a proper seal and prevent leaks. Use high-quality replacement parts recommended by the manufacturer.

    • After cleaning, perform a comprehensive fuel injector test to evaluate their performance. This test may include flow rate measurement, spray pattern examination, and leak detection. Replace any injectors that fail the test or show significant performance deviations.

    • Carefully reinstall the fuel injectors, ensuring proper alignment and connection. Follow torque specifications provided by the manufacturer to avoid overtightening or undertightening.

Regular maintenance and testing of marine fuel injectors are essential to ensure optimal engine performance and prevent potential issues. One crucial test that should be performed is the fuel injector leak test.

In the next paragraph, I will provide you with a step-by-step guide on how to perform a marine fuel injector leak test, enabling you to identify and address any leaks promptly and maintain the reliability and efficiency of your marine engine.

    1. To perform a fuel injector leak test, you will need the following items:
      • Fuel injector tester or kit
      • Appropriate safety equipment (gloves, eye protection)
      • Fuel pressure gauge
      • Fuel system cleaning solution (optional)
      • Manufacturer’s service manual (for specific instructions and specifications)

    2. Before beginning the test, it is crucial to ensure the safety of the testing environment. Follow these steps:

      • Make sure the engine is turned off and has had enough time to cool down.

      • Locate the fuel injectors on your marine engine. They are usually mounted on the cylinder head.

      • Review the manufacturer’s service manual for any specific instructions or precautions related to your engine model.

    3. To prevent fuel flow during the test, you need to disconnect the fuel supply. Follow these steps:

      • Locate the fuel supply line connected to the fuel rail or fuel distributor.

      • Carefully disconnect the fuel line using the appropriate tools, ensuring that any residual pressure is relieved safely.

      • Use a suitable plug or cap to seal the open end of the fuel line to prevent any fuel leakage.

    4. The fuel injector tester allows you to apply pressure and detect potential leaks. Follow these steps:

      • Connect the fuel injector to the fuel injector test bench according to the manufacturer’s instructions.

      • Ensure a secure and proper connection between the tester and the fuel injectors.

      • Make sure all connections are tight and leak-free to maintain accurate testing results.
    5. Now it’s time to apply pressure to the fuel injectors and observe for any leaks. Proceed as follows:
      • Refer to the manufacturer’s instructions to determine the recommended pressure for your specific engine model.

      • Connect a fuel pressure gauge to the fuel system to monitor the pressure during the test.

      • Gradually increase the pressure to the specified level while monitoring the gauge for any sudden drops or fluctuations, indicating potential leaks.

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    6. During the pressure test, carefully inspect each fuel injector for signs of leaks. Perform the following:

      • Visually inspect around each fuel injector for any fuel drips, seepage, or signs of wetness.

      • Use a flashlight if necessary to better observe the injector area and connections.

      • Pay attention to the injector O-rings, connectors, and fuel lines for any signs of deterioration or damage.

If you identify any leaks during the test, it is crucial to address them promptly. Replace any faulty O-rings or damaged injector components. Clean the fuel injectors using a suitable fuel system cleaning solution, following the manufacturer’s instructions. Re-test the fuel injectors after repairs or cleaning to ensure the leaks have been resolved.

Performing a fuel injector leak test is a crucial aspect of maintaining the performance and reliability of marine engines. By following this step-by-step guide, you can identify potential leaks early on, address them promptly, and ensure the optimal operation of your marine fuel injectors.

To maintain the optimal performance of marine fuel injectors between overhauls, consider implementing simple routine maintenance practices, like:

    • proper purifier operation and maintenance, to ensure clean and high-quality fuel, minimizing the risk of injector clogging and deposits.
    • periodically use fuel additives designed to clean and lubricate the fuel system. These additives can help remove deposits and improve injector performance.

    • conduct visual inspections of the fuel injectors during routine maintenance checks. Look for signs of leaks, damaged components, or buildup that may require immediate attention.

In conclusion, marine fuel injectors play a vital role in the performance, efficiency, and longevity of marine engines. Overhauling and maintaining these injectors ensure proper fuel delivery, optimal combustion, and reliable engine operation. By following the steps outlined in this blog post and implementing routine maintenance practices, you can maximize the performance and lifespan of your marine fuel injectors. Remember, a well-maintained fuel injector system translates into a smoother, more efficient, and trouble-free vessel operation experience.

If you want to learn and get a “Diploma in Marine Diesel Engines”, please follow THIS LINK on Alison platform. The course is free and all you need to do is just to subscribe to their platform using the link above. This will be of a great help to me as well, as I will earn small commission. You can consider this as a reward for my effort to provide guidance and advices with regard to complex, challenging and rewarding marine engineering. 

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World, Telegram Chief Engineer’s Log Chat or Instagram and will try to answer to all your queries. You can use the feedback button as well!

If you like my posts, please don’t forget to press Like and Share. You can also Subscribe to this blog and you will be informed every time when a new article is published. Also you can buy me a coffee by donating to this website, so I will have the fuel I need to keep producing great content! Thank you!

A Comprehensive Guide of Understanding Marine Propulsion Systems

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Marine propulsion systems are the driving force behind the movement of ships and vessels on the water. They are essential for powering and maneuvering various types of marine vessels, ranging from small boats to large ships. Understanding the different types of marine propulsion systems is crucial for comprehending their principles, advantages, disadvantages, limitations, and applications. In this comprehensive guide, we will explore different marine propulsion systems, including diesel engines, gas turbines, electric propulsion, nuclear systems, and hybrid systems. By gaining insights into these systems, we can better understand their capabilities and their impact on vessel performance, efficiency, and environmental sustainability.

    • Diesel Engines: Diesel engines are widely used in marine propulsion systems due to their reliability, fuel efficiency, and versatility. These engines operate on the principle of internal combustion, compressing air within cylinders and injecting fuel to ignite it. Diesel engines offer advantages such as high thermal efficiency, excellent torque characteristics, and long service life. They are suitable for various vessel types, including commercial ships, cargo vessels, and offshore support vessels. Diesel engines provide reliable propulsion, good fuel economy, and the capability to operate for extended periods, making them a popular choice for long-haul voyages and heavy-duty applications. However, they emit greenhouse gases and require regular maintenance.

      Example of marine diesel engine

    • Gas Turbines: Gas turbines are known for their high power-to-weight ratios and rapid acceleration capabilities, making them ideal for high-speed vessels. These propulsion systems work by converting the energy from burning fuel into rotational motion. Gas turbines offer advantages such as quick response times, compact size, and lightweight construction. They find applications in naval vessels, high-speed ferries, and other vessels where speed is a priority. Gas turbines provide fast acceleration, high power output, and the ability to operate in harsh environments. However, they have higher fuel consumption and emissions compared to diesel engines, limiting their efficiency for long-haul voyages.

      Example of marine gas turbine engine. Source and credit: Wartsila

    • Electric Propulsion: Electric propulsion systems have gained popularity due to their environmental benefits, enhanced maneuverability, and reduced noise levels. These systems utilize electric motors to drive the vessel’s propellers, powered by energy sources such as batteries, fuel cells, or generators. Electric propulsion offers advantages such as lower emissions, improved fuel efficiency, and quieter operation. It is particularly suitable for smaller vessels, including yachts, research ships, and ferries operating in environmentally sensitive areas. Electric propulsion provides precise control, maneuverability, and the ability to operate at variable speeds, making it valuable for dynamic positioning and station-keeping operations. However, electric propulsion may have limited range and requires adequate power supply and storage infrastructure.

Example of electrical propulsion engine. Source and credit: Siemens Energy Global

    • Nuclear Systems: Nuclear propulsion systems use the energy generated from nuclear reactions to produce steam and drive turbines, which in turn power the vessel’s propulsion systems. Nuclear systems offer advantages such as high power output, long operational duration, and reduced dependency on fossil fuels. They find applications in naval vessels, such as aircraft carriers and submarines, where extended endurance and high power are essential. Nuclear propulsion systems provide significant propulsion capabilities and eliminate the need for frequent refueling. However, they require specialized infrastructure, stringent safety measures, and proper disposal of nuclear waste.

      Example of electrical propulsion engine. Source and credit: Pinterest

    • Hybrid Systems: Hybrid propulsion systems combine multiple power sources, such as diesel engines, gas turbines, and electric motors, along with energy storage systems, to optimize efficiency and reduce environmental impact. These systems offer advantages such as reduced fuel consumption, lower emissions, increased redundancy, and improved flexibility. Hybrid propulsion finds applications in a variety of vessels, including offshore support vessels, ferries, and cruise ships. They allow for optimal utilization of power sources based on operational requirements, providing efficient propulsion and environmental sustainability. However, hybrid systems may have higher initial costs and require sophisticated control and integration mechanisms.

      Schematic of a hybrid propulsion system. Source and credit: Marine Link

In conclusion, understanding marine propulsion systems is essential for comprehending the complexities of ship design, performance, and environmental impact. Diesel engines, gas turbines, electric propulsion, nuclear systems, and hybrid systems each have their own principles, advantages, disadvantages, limitations, and applications. From the reliability and fuel efficiency of diesel engines to the speed and acceleration capabilities of gas turbines, and the environmental benefits of electric propulsion and hybrid systems, the choice of propulsion system depends on various factors such as vessel type, operational requirements, and environmental considerations. By embracing technological advancements and sustainable practices, the maritime industry can continue to improve propulsion systems, ensuring efficient, environmentally friendly, and safe transportation across our oceans.

If you want to learn more about Marine Diesel Engines, please follow THIS LINK on Alison platform. The course is free and all you need to do is just to subscribe to their platform using the link above. This will be of a great help to me as well, as I will earn small commission. You can consider this as a reward for my effort to provide guidance and advices with regard to complex, challenging and rewarding marine engineering. 

If you wish to learn about “ Principles and Constructional Features of Gas Turbines”, please follow THIS LINK.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World, Telegram Chief Engineer’s Log Chat or Instagram and will try to answer to all your queries. You can use the feedback button as well!

If you like my posts, please don’t forget to press Like and Share. You can also Subscribe to this blog and you will be informed every time when a new article is published. Also you can buy me a coffee by donating to this website, so I will have the fuel I need to keep producing great content! Thank you!

What do you need to know about “Visatron” oil mist detector

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Oil mist detectors are devices that are meant to protect large diesel engines of all applications against serious damage originating from crank-drive bearings or piston components overheating.

 

 

In case of “Visatron” oil mist detector, the atmosphere of the crankcase compartment is continuously drawn out by means of header pipes sampling system from each crankcase compartment and directed through an optical opacity measuring track.

The suction vacuum required is generated through a wear-free air jet pump in the device, fed with the compressed air (drive air), usually from engine control air system.

The sample flow, consisting of the drawn in atmosphere of the crankcase compartment, is guided through an optical channel for measuring turbidity (opacity). The sample flow is measured by absorption of infrared light.

Opacity percentage is used as the dimensional unit of the turbidity:

    • 100 % opacity means total absorption
    • 0% opacity means no absorption

Oil mist becomes explosive from a concentration of approx. 50 mg of atomized oil in 1 liter of air and up, which correspond to an opacity of approx. 40 %. To learn more about this, please follow this link.

The alarm level sensitivity for different models of “Visatron” oil mist detectors are as per below table:

These devices are very reliable and require minimum maintenance from the crew side.

However, there are some periodical performance test and calibration that are required in order to ensure that the device is working as intended and to ensure the best protection for your engine.

The performance test and calibration must be done when the engine is stopped and vessel is at anchor or safely moored in port.

You must be aware that during the performance test the engine is not monitored by the oil mist detector.

The performance test is done following the below steps (here there is an example for Visatron VN 93 model):

    • Open the control cover for the measuring head

    • Wait until the READY-LED is switched off (approx. 10 sec)

    • As above the following display appears.
    • Blind the light beam of the measuring track with a wooden vane or a similar object.

    • At devices VN 116/93 and VN 215/93 the damage check starts on the display damage compartment as can be seen in the above picture.
    • When the alarm level is reached the TEST-LED lights up (TEST-ALARM). To set back the TEST-ALARM touch the ENTER-RESET button for more than 1 second and TEST-LED goes off.
    • Close the control cover of the measuring head.
    • After approx. 15 seconds the device is back in the normal operation.

A live test with test vapour can be carried out at the engine stand still when vessel is at anchor or safely moored in port.

The test is done as follow:

    • Open the crankcase or, more convenient, disconnect one of the sampling pipes which leads to the oil mist detector.
    • By using a smoke detector test spray, spray a short burst of vapour into the pipe or inside crankcase collecting funnel.
    • Allow the oil mist detector to draw the vapours for minimum 20 seconds.
    • Depending of the vapour density and suction time, whether an oil mist alarm is triggered or an oil mist alarm is triggered and a search run starts on the display damage compartment (VN 215/93 model).

As a maintenance, the requirements are as follow:

  • Monthly maintenance: check the negative pressure in the measuring head (range 60 – 80 mm H2O).
      • The negative (suction) pressure must be calibrated by adjusting the pressure regulator when the engine is at a standstill.
      • Make sure engine room ventilation is in operation (pressure difference in engine room)
      • Pour water inside the U-tube manometer utilizing the bottle from the service box. Both tubes shall be filled equally to the half of the scale of the manometer and must be on the same level when the manometer is not connected to the oil mist detector.
      • Loosen nut (1) and turn setscrew (2) in clockwise direction slowly up to the stop.

      • Open safety cover (3) at the throttle (5) and manually turn the setscrew (4) in clockwise direction slowly up to the stop.
      • Make sure that compressed air is open (7 bar)
      • Connect the U-tube manometer to the oil mist detector quick connection as below and it should show 0 pressure.

      • Turn setscrew (4) in counterclockwise direction until the U-tube manometer indicates a negative pressure of 80 mm H2O
      • Close safety cover
      • Turn setscrew (2) in counterclockwise direction until the negative pressure is only 60 mm H2O

      • Tight counter nut (1)
      • Disconnect U-tube manometer.
  • Quarterly maintenance:
      • replace the sintered bronze filters in the measuring head. The filters must be replaced and not cleaned.

        • clean the infrared filter glasses in the measuring head. Use only cotton buds to clean these filter glasses as there is a risk of scratching those.

  • Six monthly maintenance ( only on devices equipped with optional siphon block): remove siphon block plug and blow clean with compressed air (max. 7 bar).
  • Annually maintenance: replace sintered bronze filter in the pressure reducer.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World and will try to answer to all your queries.

If you like my posts, please don’t forget to press Like and Share. You can also Subscribe to this blog and you will be informed every time when a new article is published. Also you can buy me a coffee by donating to this website, so I will have the fuel I need to keep producing great content! Thank you!

 

Source and Bibliography:

  • Source and credit:  Schaller Automation

What you need to know about Sulzer RT-Flex engine

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The Sulzer RT-flex engine is essentially a standard Sulzer RTA slow-speed two-stroke marine diesel engine except that, instead of the usual camshaft and its gear drive, fuel injection pumps, exhaust valve actuator pumps, reversing servomotors, and all their related mechanical control gear, the engine is equipped with a common-rail system for fuel injection and exhaust valve actuation and full electronic (computer) control of engine functions. Two control oil pumps are provided near the engine local control stand, and one of these must always be operational to ensure that the common rail fuel and exhaust valve operation systems can function. The control pump starts automatically once one of the crosshead lubricating oil pumps is started.

The engine is monitored and controlled by a WECS (Wartsila Engine Control System) unit. This is a modular electronic system with separate microprocessor control units for each cylinder. Overall control and supervision is by means of separate, duplicate microprocessor control units.

The cylinder microprocessor control units are mounted on the front of the engine at the common rail in the hot-box, which is located below the top engine platform.

The engine is a single-acting, two-stroke, reversible, diesel engine of crosshead design with exhaust gas turbocharging and uniflow scavenging. Tie rods bind the bedplate, columns and cylinder jacket together. Crankcase and cylinder jackets are separated from each other by a partition, which incorporates the sealing gland boxes for the piston rods. The cylinders and cylinder heads are fresh water cooled.

The exhaust gases flow from the cylinders through the hydraulically operated exhaust valves into a manifold and then on to the exhaust gas turbochargers which work on the constant pressure charging principle.
The charge air delivered by each turbocharger flows through an air cooler and water separator into the common air receiver. Air enters the cylinders through the scavenge ports, via valve groups, when the pistons are nearly at their bottom dead centre (BDC) positions. At low loads two electrically-driven auxiliary blowers supply additional air to the scavenging air space.

The pistons are cooled by bearing lubricating oil supplied to the crossheads by means of articulated lever pipes. The thrust bearing and turning gear are situated at the engine driving end. The fuel and servo oil pumps for the common rail fuel system and exhaust valve actuation are driven by gearwheels from the crankshaft.

The engine is started by compressed air, which is controlled by the electronic starting air system. In case of failure of the engine remote control system (from the bridge or the engine room telegraph) the engine can be controlled from a local (emergency) control stand located on the port side of the engine on the middle platform. There is an ECR back-up control system which is linked with the local (emergency) control system.

The engine lubrication system, with the exception of turbocharger and cylinder lubrication, is supplied by one of two main pumps, which take suction from the main engine lubricating oil sump tank and supply the main bearings. The engine main bearings and thrust block are supplied with lubricating oil by the duty main lubricating oil circulation pump. There are two pumps fitted and these are located at the aft end of the engine with one working and the other switched to automatic standby. The oil is cooled before supply to the engine. Oil from the main bearing system is also supplied, via articulated lever pipes, to cool the working piston crowns. The main bearing and crosshead oil systems are interconnected as the crosshead pumps take their suction from the main bearing LO supply line to the engine.
Two crosshead LO pumps, one working and one on standby, take their suction from the main LO supply to the engine, after the automatic backflush filter and supplies oil at increased pressure to the crosshead bearings and to the servo oil pumps. The bottom end bearings are also supplied with LO from the associated crosshead with the oil flowing down a bore in the connecting rod. The lubrication of crossheads and connecting rod bottom end bearings is made through articulated lever pipes.

The turbochargers are supplied with lubricating oil from the turbocharger LO system. There are, usually two or three turbocharger LO pumps (depending of the engine size and design), one/two operating and one on automatic standby. These pumps supply oil to the turbocharger bearings from the turbocharger LO sump tank via a cooler. The pumps have suction filters and there is also an automatic backflushing filter unit with a back-up bypass filter.

With regard to cylinder lubrication more information can be found on this link.

The fuel oil is supplied to a common rail by the fuel supply pumps which are driven from the crankshaft by a gear system. The fuel pumps are arranged in a V form with four pumps in each bank. The pumps deliver pressurised fuel oil to a collector which then supplies the common fuel rail which is maintained at a pressure of about 1,000 bar at full load (the actual pressure varies with engine load). Recently, for safety and operational reasons the pressure has been reduced to 600 bars. All parts of the high pressure fuel system are sheathed to prevent high pressure fuel leakage from entering the engine room spaces. The fuel supply pumps are driven by a camshaft via three-lobed cams. The lobed cams and the speed of the camshaft means that each pump makes several strokes during a crankshaft revolution. There are six or eight fuel supply pumps (depending on the engine size) and the output of the pumps is such that seven pumps have the capacity to meet the full load requirements of the engine. With only six pumps operational, the engine load must be reduced below maximum. The common fuel rail is divided into two equal sections, one serving the forward six cylinders and the other serving the six aft cylinders. The common rail volume is such that the fuel pressure is constant throughout the operation of the engine.

There are three fuel injectors fitted in each cylinder cover and high pressure fuel oil is supplied to these from the common rail. Each cylinder has its own injection control unit which controls the fuel supply to the injectors from the common fuel rail. Each injection control unit has three rail valves and three injection control valves, one of each for each injector. The rail valve is an electrically operated spool valve which can be moved to each end of its casing by electrical signals from the WECS. The spool valve acts as an open or closed valve and when in the open position it directs control oil to the injection control valve. The injection control valve opens and allows high pressure fuel from the common rail to pass to the fuel injector so beginning fuel injection at that injector. When the WECS signals the spool valve to close, the injection control valve is closed and hence fuel injection stops. Control oil is supplied by the servo and control oil manifold at a pressure of 200 bar. The rail valves are bi-stable solenoid valves with a fast actuation time; the valve is not energised for more than 4ms at any time.

The WECS controls the fuel injection system via the Flex Control Module (FCM-20) which not only regulates the start and end of injection but also monitors the quantity of fuel injected. The fuel quantity sensor measures the actual amount of fuel injected and this information is relayed to the control system. The control system then calculates any change in fuel timing required from the engine operating conditions and the actual fuel quantity injected. The functioning of the fuel injection system is monitored at each cycle and changes are made for the next cycle if necessary.
Operation of the rail valves is under the control of the WECS, which can adjust the timing and quantity of fuel injection to suit operating conditions.
Normally all three cylinder fuel injectors, which are of the hydraulically actuated type, operate together but as they are independently controlled it is possible for them to be programmed to operate separately. In the event of one of the fuel injectors or its actuation system failing, the engine may continue to operate with the remaining two injectors. At low engine speeds one or two of the fuel injectors can be cut out for each cylinder to minimise exhaust smoke.
The remaining operational fuel injector(s) operate at longer injection periods with the high fuel pressure maintained by the common rail. With injector(s) cut out the operating injector(s) are changed over every 20 minutes to prevent overheating of the cut out injector(s) and to ensure that all of the injectors have equal running.
The fuel quantity delivered to the engine by the fuel preparation unit is considerably greater than is actually required by the engine with the excess flowing back to the mixing unit of the main fuel preparation unit. The mixing unit is located at the FO circulating pump suction and also takes a FO feed from the low pressure FO supply pump which draws HFO from the duty HFO service tank. From the circulating pumps the HFO flows through the steam heaters and then to the supply manifold for the high pressure common rail supply pumps. A pressure regulating valve, set at 10kg/cm² is fitted between the engine FO inlet and outlet lines and this allows the correct fuel oil supply pressure to be maintained at the engine inlet.
The main engine is designed to operate on HFO during manoeuvring. All pipes are provided with trace heating and are insulated. For reasons of safety, all high-pressure pipes are encased by a metallic hose. Any leakage is contained and led to an alarmed fuel oil leakage tank. The engine may be operated on MDO if necessary.

The starting air system of the RT-flex engine is similar to that of a standard RTA engine except for the control of the cylinder starting air valves which is incorporated in the WECS rather than a starting air distributor. Starting air is supplied to the engine starting air manifold from the starting air receivers via the starting air shut-off valve. The individual cylinders are then supplied with starting air via branch pipes which have flame arresters fitted.
The cylinder starting valve is operated by pilot air and the pilot air valve is controlled electrically by the cylinder control module. The starting pilot air valve is opened and closed directly by the Flex control module (FCM-20) once every revolution at defined crank angles during the starting period. When the engine has started the starting system is shut down.

Each cylinder has a single exhaust valve centrally located in the cylinder cover which is hydraulically opened, but closed by air pressure acting on the piston located below the hydraulic actuating cylinder. When hydraulic pressure is applied to the actuating piston to open the exhaust valve, the air trapped below the air piston is compressed. When the hydraulic opening pressure is removed the air pressure acts on the piston to close the exhaust valve and this is known as the ‘air spring’. The space above the air piston is vented and make-up air is supplied to the space below the piston from the control air system via a non-return valve to replace any leakage that may have occurred.
The exhaust valve is fitted with a series of vanes on the stem known as a spinner. When the exhaust valve is opened, exhaust gas escaping from the cylinder acts on the spinner and causes the valve to rotate. Rotation of the valve evens out the temperature of the valve, and as the valve is still rotating when it reseats it creates a light grinding effect which removes deposits from the valve seat and valve face.
The FCM-20 controls the exhaust valve opening and closing. Hydraulic pressure for opening the valve comes from the servo oil common rail. This is pressurised to 200 bar by the servo oil pumps which are driven by the same gear drive system as the fuel common rail pumps. The FCM-20 controls an exhaust rail valve which then activates the exhaust hydraulic control slide valve and this directs hydraulic oil to and from the exhaust valve actuator unit. The servo oil acts on the lower face of the free-moving exhaust valve actuator piston and as the piston moves upwards, when servo oil pressure is applied, it exerts an hydraulic force on the exhaust valve piston and opens the exhaust valve.
The hydraulic system connecting the upper face of the exhaust valve actuator piston with the exhaust valve piston (the hydraulic pushrod) is filled with engine bearing oil and a connection with the bearing circulation system ensures that the space is always fully charged. This arrangement provides a complete separation of servo hydraulic system and valve actuation/bearing lubricating oil systems, and enables the exhaust valves to be serviced without disturbing the servo oil system.

The RT-flex engine control is shared between the WECS internal engine control and the external propulsion control systems which comprise the remote control system, the safety system, the electronic governor and the alarm monitoring system.

The WECS is the core engine control. It processes all actuation, regulation and control systems directly linked to the engine:

      • Common rail monitoring and pressure regulation
      • Fuel injection, exhaust valve and starting air valve control and monitoring
      • Interfacing with the external systems via the CAN-open or MOD-bus
      • Engine performance tuning, IMO setting and monitoring

The WECS modules are mounted directly on the engine and communicate via an internal CAN-bus. Operator access to the WECS-9520 is integrated in the user interface of the propulsion control system. The manual control panels and the flexView system allow for additional communication with the WECS. The flexView software allows the operator to communicate with the WECS and enables the operator to see operating parameters as required.
Each engine cylinder has its own module for all cylinder related functions; all common functions are shared between the cylinder modules.

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Source and Bibliography:

  • YouTube video credit: Brian Johannesen; Marine Tech Hub; Marine Engineer (PARAMI);